This invention relates to an ultraviolet ray irradiation apparatus by the use of a dielectric barrier discharge lamp (may be referred to as an excimer lamp) which washes and modifies a surface of semiconductor, metal, or macromolecular compound and the like.
The dielectric barrier discharge lamp (excimer lamp) has different wavelength with respect to emitted light beams in accordance with the kinds of gases sealed in a lamp tube. For example, a light beam having center wavelength of 172 nm, 222 nm and 308 nm is emitted when a sealed gas is xenon, krypton chloride, and xenon chloride, respectively.
In particular, the dielectric barrier discharge lamp sealed with the xenon emits a light beam having wavelength of 172 nm as a vacuum ultraviolet light beam. To this end, when irradiation is carried out in atmosphere containing oxygen, oxygen molecular (O2) absorbs the light beam, and generates active oxygen species, such as, oxygen atom (O) and ozone (O3).
Further, photon energy of a light beam having wavelength of 172 nm is about 7.2 eV, and is higher than combination energy of a plurality of organic substances. In consequence, chemical bonds of organic compound can be cut by irradiating the light beam of 172 nm, and oxidation decomposition removal can be performed by the generated active oxygen species.
This method has been known as an UV ozone cleaning method, and been widely applied in a manufacturing process of a semiconductor integrated circuit or liquid crystal as an organic substance washing method. Further, practical use has been proceeded as a method for removing metal contamination about a method for generating chlorine radical by irradiating the ultraviolet light beam to chlorine gas, for generating chloride by reacting the chlorine radical with metal attached to a substrate surface, and for volatilizing and removing by utilizing difference of vaporizing pressure, or a method for irradiating the ultraviolet light beam to gas containing fluorine and for removing a natural oxide film on a silicon wafer by the generated fluorine radical.
The semiconductor integrated circuit is increased in its integration every year, and a permitted level of the organic compound contamination is also enhanced in a manufacturing process of the integrated circuit. Recently, the silicon wafer as the substrate of the integrated circuit mainly has a diameter of 200 mm, and a diameter of 300 mm has been gradually applied.
When the dielectric barrier discharge lamp is used to remove the organic substance contamination, a plurality of dielectric barrier discharge lamps must be arranged so as to irradiate the light beam into substrates having these sizes. For example, an apparatus, in which a plurality of lamps 120 having a length of 230 mm are used with desired spaces, has been commercially used as the ultraviolet ray irradiation apparatus for the silicon wafer having the diameter of 200 mm, as illustrated in FIG. 1A and FIG. 1B. In the ultraviolet ray irradiation apparatus of such a surface irradiating block system, as a size of a substance to be processed and be irradiated is larger, the number of the lamps is higher from necessity for irradiating the light beam throughout the substance to be processed.
However, when the number of the lamps is plural as an example illustrated in FIG. 1, it is necessary to replace old lamps due to the lamps"" lifetime with a required number of new lamps.
Further, if a plurality of lamps are used, the same number of lamp driving (lightning) circuits are required, and cost thereof becomes excessively high. Moreover, looking at plural lamps in terms of uniformity of irradiation, intensity of irradiated light beams differs directly under the lamps and in-between the lamps. Therefore, even if a reflection mirror is provided, nonuniformity of light quantity inevitably takes place for the light beam irradiated into the substance to be processed.
There is a method for performing irradiation by lineally scanning the substance to be processed or the dielectric barrier discharge lamp by the use of a single dielectric barrier discharge lamp as means for solving such a problem. The cost for the replacement due to the lamp lifetime can be reduced in this method because only single dielectric barrier discharge lamp is used. In addition, the light quantity of the light beam irradiated into the substance to be processed can be uniform because the single lamp is lineally scanned.
However, the ultraviolet light beam must be irradiated for an entire region of the substance to be processed in the method for lineally scanning the substance or the lamp. Consequently, a distance for scanning them must be equal or more to the diameter of the substance to be processed.
Further, a supporting mechanism, such as, a guide rail, becomes necessary at both sides thereof because the dielectric barrier discharge lamp is lineally scanned. As a result, the apparatus becomes large and expensive.
Moreover, it is difficult to tightly cover between the dielectric barrier discharge lamp and the substance to be processed, and is difficult to use corrosive gas, such as, chlorine gas and fluorine gas.
Due to the above-mentioned reasons, suggestion has been made about an apparatus in which the substance to be processed is rotatably supported on a supporting stand, and a process is carried out by relatively rotating the substance for the dielectric barrier discharge lamp (for example, see Japanese Unexamined Patent Publication (JP-A) No. H09-92634).
An apparatus structure can be simplified in the conventional apparatus in comparison with the case that the dielectric barrier discharge lamp is lineally scanned. Thereby, downsizing of the apparatus becomes possible.
On the other hand, when the ultraviolet light beam is given for the substance to be processed by rotating the irradiating range, a relative speed between the substance and the lamp is variable in accordance with a distance from the rotating center. Therefore, when irradiating light quantity for a length direction of the dielectric barrier discharge lamp is constant, as the distance from the rotating center becomes larger, the integrating light quantity for the surface of the substance becomes smaller. As a result, the surface process can not be uniformly carried out.
To solve this problem, a light shielding plate, in which a region (hereinafter, referred to as an ultraviolet light passing region) for passing the ultraviolet light beam of substantially triangle shape is formed, is arranged in a method described in FIG. 5 and description in the above-mentioned Japanese Unexamined Patent Publication (JP-A) No. H09-92634. Thereby, the integrating light quantity of the ultraviolet light beam, which reaches the surface of the substance to be processed, is adjusted in accordance with the distance from the rotating center.
However, when the irradiation of the ultraviolet light beam is performed through the above-mentioned ultraviolet light passing region of the triangle shape, it has been confirmed by inventor""s experiment that the integrating light quantity on the surface of the substance to be processed does not accurately become constant in accordance with the distance from the rotating center.
This is because the light intensity for width direction of the dielectric barrier discharge lamp 11 distributes to an angled shape, and is not constant, as illustrated in FIG. 4A. In the experiment, such a result that the integrating light quantity becomes smaller in accordance with the distance from the rotating center has been obtained. From this fact, when the shielding plate of the triangle shape is used, the uniform surface process can not be performed.
It is therefore an object of this invention to provide an ultraviolet ray irradiation apparatus which is capable of approaching integrating light quantity of an ultraviolet light beam for a surface of a substance to be processed constant when an ultraviolet light beam is irradiated by relatively rotating the substance for a dielectric barrier discharge lamp, and thereby, enhancing uniformity of a surface process.
To achieve the above-mentioned object, an ultraviolet ray irradiation apparatus which performs washing and modification by irradiating an ultraviolet beam for a surface to be processed of an substance to be processed according to this invention comprises a dielectric barrier discharge lamp which has a length of a maximum diameter of the surface or more, a turntable which mounts the substance such that the surface is placed under irradiation of the ultraviolet light beam irradiated by the dielectric barrier discharge lamp, a rotation center thereof substantially corresponding to a center of an irradiating range of the ultraviolet light beam due to the dielectric barrier discharge lamp, a driving source which rotates and drives the turntable, and a filter which is fixed under the irradiation of the ultraviolet light beam due to the dielectric barrier discharge lamp and which adjusts light quantity of the ultraviolet light beam that reaches the surface of the substance in accordance with shapes of an ultraviolet beam passing region, the shape of the ultraviolet light beam passing region being symmetrical for a center line for a length direction of the irradiating range of the ultraviolet light beam, and at least a portion near a center of the irradiating range of the ultraviolet light beam of each line segment that forms a boundary of the ultraviolet light beam passing region in a width direction of the ultraviolet light beam passing region being substantially expressed by a quadratic curve that a distance r in the length direction of the irradiating range of the ultraviolet light beam on the basis of the center line is variable.
Whereby, the irradiation due to the dielectric barrier discharge lamp is performed by relatively rotating the substance for the dielectric barrier discharge lamp. Thereby, the ultraviolet light beam is irradiated from the dielectric barrier discharge lamp for an entire region of the surface.
In this case, at least the portion near the center of the irradiating range of the ultraviolet light beam of each line segment that forms the boundary of the ultraviolet light beam passing region in the width direction of the ultraviolet light beam passing region is preferably given by a curve m (r) which is based on the center line for the width direction of the irradiating range of the ultraviolet light beam and in which extension thereof passes near the center of the irradiating range, integrating light quantity E (r) given by the following equation in a direction along the center line being substantially constant,                               E          ⁡                      (            r            )                          =                              t            ·                                          ∫                0                                  m                  ⁡                                      (                    r                    )                                                              ⁢                                                [                                      4                    ·                                          P                      ⁡                                              (                        s                        )                                                                              ]                                ⁢                                  xe2x80x83                                ⁢                                  ⅆ                  s                                                                          2            ⁢            π            ⁢                          xe2x80x83                        ⁢            r                                              (        1        )            
P(s): light intensity of the dielectric barrier discharge lamp;
s: a distance in a width direction from an axis line of the dielectric barrier discharge lamp;
r: a distance from the rotation center of the substance.
Further, it is preferable that the line segments that form the boundary in the width direction of the ultraviolet light beam passing region does not reach the center of the irradiating range of the ultraviolet light beam, and are combined by adjacent line segments to each other in the width direction of the ultraviolet light beam passing region, thereby, two ultraviolet light beam passing regions apart with desired distance being formed at both sides of the center of the irradiating region.
Moreover, the ultraviolet light beam passing region is preferably a slit which is opened in the filter.
This invention further comprises at least a process chamber which tightly covers the irradiating range of the ultraviolet light beam due to the dielectric barrier discharge lamp from an external.
This invention further comprises a body of equipment which contains at least the turntable and the driving source, an upper side thereof being opened, and a cover which is attached so as to open and close the opening for the body and which is fixed with at least the dielectric barrier discharge lamp and the filter.
In this event, the process chamber, which is tightly covered from the external, is preferably formed by closing the cover for the body.